Power System Computer Aided Design Research Articles

Evaluation of Power System Lightning Performance—Part II: Application to an Overhead Distribution Network

The paper aims at defining a methodology to evaluate the lightning performance of a system of overhead distribution lines. As is well known, the evaluation of the lightning performance relies generally on a Monte Carlo approach that generates many different lightning events and calculates the corresponding overvoltages. To perform such calculation, the power system computer aided design (PSCAD) module developed in the companion paper is adopted. However, as any call to PSCAD implies a nonnegligible computational effort, here an efficient approach is presented in order to limit the number of simulations as much as possible. The obtained results are compared with the ones provided by other available techniques both on simple structures in order to highlight the main features of the method and on a typical Italian distribution network segment. The comparative analysis shows good agreement between the methods and the effectiveness of the proposed technique in terms of computational effort reduction.

Impact of series compensation on operation performance of large‐scale PV plants

Application of series compensation transmission lines to enhance the long-distance transmission capability of photovoltaic (PV) plants is the most economical technical measure. To investigate the impact of series compensation on operating performance of large-scale PV plants, the simulation research is performed in this study. The detailed model of large-scale PV plants connected to the grid through series compensated lines is developed using power systems computer aided design (PSCAD)/electromagnetic transients inccluding DC (EMTDC) software. Using the detailed model, the performances of active and reactive power outputs, voltage and current profiles of PV plants are investigated for different levels of series compensation and strengths of AC system during short-circuit faults. The simulation results show that series compensation and strong AC system can effectively improve the transient operation performance of the PV power plant. With the increase of the series compensation degree and the strength of AC system, the fault ride-through performance of PV plants is improved.

A conventional dynamic voltage restorer with fault current limiting capability

In this paper, a new topology of conventional dynamic voltage restorer (DVR) with fault current limiting capability is proposed. The structure uses a grid-tied transformer which is utilized for both supplying energy to the DVR, and revers voltage supply as a FCL function. In order to limit the fault current, a fast bidirectional switch is employed during fault condition to supply revers voltage to avoid high current levels. However, the ratio of transformer is consequential for the proper operation. Also, for decreasing power losses across isolation transformer and semiconductors, a switch is added to flow the current during normal state. The design methodology of the proposed structure is discussed and the results are carried out based on power systems computer aided design (PSCAD)/electromagnetic transients including dc (EMTDC) simulation.

Wide‐band modelling and transient analysis of the multi‐conductor transmission lines system considering the frequency‐dependent parameters based on the fractional calculus theory

The transient analysis of multi-conductor transmission lines should consider the frequency-dependent characteristics due to the skin effect. Fully considering the inherent fractional order characteristics of the frequency-dependent effect, a general wide-band modelling method is proposed. The fractional order vector fitting method is adopted to approximate the frequency-dependent parameters and the corresponding fractional differential equations can be obtained by the inverse Laplace transformation. The backward difference is a practical method to solve the fractional differential equations; however, a linear convolution must be calculated, which will lead to a heavy computation complexity. To address this issue, a new recursive convolution method for the fractional differential equations is proposed and an efficient solution is achieved. Furthermore, considering the indispensability of the passivity verification of a system for the transient simulation, the passivity verification by extending the Hamiltonian matrix for the fractional order systems is studied and a practical criterion is proposed. Three examples are considered to validate the proposed method: (i) a single underground cable, (ii) three-phase underground cable, and (iii) an experimental transformer under very fast transient voltage. The simulation results are compared with the results obtained by power systems computer-aided design or measurements and good agreements are achieved.

Algorithm for transformer differential protection based on wavelet correlation modes

In this study, a new algorithm for discrimination between internal faults and inrush current conditions in power transformers is presented. First, the proposed algorithm removes the pre-fault conditions of the fault currents. Then, those currents are processed using the discrete wavelet transform to obtain the wavelet matrix. The correlation matrix is computed from wavelet matrix to know the eigenvalues associated with each frequency scale and to reduce the analysed information. This algorithm, which the authors are going to call wavelet correlation modes, is used to identify inrush and internal fault currents in power transformer. To validate the proposed algorithm, simulations are carried out in power systems computer-aided design software, and the obtained signals are analysed in order to evaluate its performance and sensitivity.

A Novel Protection Method for Single Line-to-Ground Faults in Ungrounded Low-Inertia Microgrids

This paper proposes a novel protection method for single line-to-ground (SLG) faults in ungrounded low-inertia microgrids. The proposed method includes microgrid interface protection and unit protection. The microgrid interface protection is based on the difference between the zero-sequence voltage angle and the zero-sequence current angle at the microgrid interconnection transformer for fast selection of the faulty feeder. The microgrid unit protection is based on a comparison of the three zero-sequence current phase directions at each junction point of load or distributed energy resources. Methods are also included to locate the minimum fault section. The fault section location technology operates according to the coordination of microgrid unit protection. The proposed method responds to SLG faults that may occur in both the grid and the microgrid. Simulations of an ungrounded low-inertia microgrid with a relay model were carried out using Power System Computer Aided Design (PSCAD)/Electromagnetic Transients including DC (EMTDC).

Improvement in Stability of HVDC System by Optimizing PI Control Parameters in PSCAD

Background/Objectives: The stability of High-Voltage Direct Current (HVDC) system is improved by optimization of system's control parameters. The simulation model of HVDC network is designed in Power Systems Computer Aided Design (PSCAD) and the Proportional Integral (PI) parameters optimization are achieved by using simplex algorithm. Simulation based evaluation of Integral Time Absolute Error-Objective function (ITAE-OF) is implemented in this paper. Methods/Statistical Analysis: Simulation calculation results are iterated to determine the new values of objective function. The model of three parallel HVDC lines connecting Power system of Central-East China is used as a test network. PI control parameters of San-Chang ±500KV HVDC system line are optimized. Findings: Optimized results have been achieved by evaluating ITAE-OF using transient simulation and converged via Simplex algorithm in PSCAD. The performance of system in steady state behavior as well as in fault condition is improved through optimized control parameters as compared to the initial control parameters, which are presented by plotting graphs. Application/Improvements: The derived equation can be further optimized using the hybrid system.

Operation and control of an insulated gate bipolar transistor‐based current controlling device for power flow applications in multi‐terminal high‐voltage direct current grids

One of the main problems that need to be solved to allow the realisation of multi-terminal high-voltage direct current (HVDC) transmission systems is the absence of a practical power flow control method. Industry leaders and researchers have proposed a few methods of power flow control based on either the control of converter station or the connection of new power electronic equipment to the grid. This study presents the operation and control of a three-port insulated gate bipolar transistor-based current flow control (CFC) device suitable for multi-terminal HVDC systems. Key features and functionalities of the proposed controller including the balancing of cable currents, limiting the magnitude of cable current and current nulling are demonstrated. The three-port CFC was simulated using power system computer aided design (PSCAD)/electromagnetic transient and direct current (EMTDC), network simulation software to evaluate its steady state and dynamic performance. Furthermore, low-power prototypes are implemented for a two and three-ports CFC to experimentally validate their different functionalities. Simulation and experimental studies explore the fast dynamic response and the results show that the CFC studied may have a significant role to play in the control of power flows in multi-terminal high-voltage DC systems.

Optimal Placement of Unified Power Flow Controller by Dynamic Implementation of System-Variable-Based Voltage-Stability Indices to Enhance Voltage Stability

Abstract A new approach of unified power flow controller (UPFC) optimal placement in the power system network based on dynamic analysis of voltage stability is presented in this paper. Voltage stability indices (VSIs), called line stability index LQP, voltage collapse point indicators (VCPIs), and line stability factor Lmn have been employed to explore the most suitable location for UPFC. The locations of UPFC are identified by dynamically varying loads across all the PQ buses by different percentages to satisfy the real power system conditions. The simulations are conducted in a power system computer-aided design (PSCAD) environment where IEEE-39 bus system has been chosen as case study. The effectiveness of the proposed method has been ensured from the simulation results because UPFC's placement in the obtained locations resulted in an improved voltage stability condition. Furthermore, to verify the suitability of the explored locations, a comparative study has been conducted after placing UPFC in the present locations and other locations obtained using optimization techniques like particle swarm optimization (PSO), differential evolution (DE), genetic algorithm (GA), and bacteria foraging algorithm (BFA). In all the cases, UPFC's placement in the identified locations using the proposed approach has resulted in better voltage stability condition improvement compared to heuristics approaches.

RT-HIL Implementation of the Hybrid Synchrophasor and GOOSE-Based Passive Islanding Schemes

Real-time hardware-in-the-loop performance assessment of three different passive islanding detection methods for local and wide-area synchrophasor measurements is carried out in this paper. Islanding detection algorithms are deployed within the phasor measurement unit (PMU) using logic equations. Tripping decisions are based on local and wide-area synchrophasors as computed by the PMU, and trips are generated using IEC 61850-8-1 generic object-oriented substation event messages. The performance assessment compares these islanding detection schemes for the nondetection zone and operation speed under different operating conditions. The testbench that is demonstrated is useful for a myriad of applications where simulation exercises in power system computer-aided design software provide no realistic insight into the practical design and implementation challenges. Finally, different communication latencies introduced due to the utilization of synchrophasors and IEC 61850-8-1 GOOSE messages are determined.

A New Algorithm for Busbar Fault Zone Identification Using Relevance Vector Machine

This article presents relevance vector machine (RVM) based relaying scheme for busbar protection which correctly differentiates between internal faults on busbar and external faults. To validate the proposed scheme, numerous computer simulations have been carried out on an existing 220 kV Indian power generating station having different types of bays such as line, transformer, reactor & generator with generator transformer (GT). Various fault conditions (test data set of 23,760) have been simulating using the power system computer aided design (PSCAD)/ electromagnetic transient direct current (EMTDC) software package (Winnipeg, MB, Canada) by varying fault & system parameters. The proposed RVM based fault discrimination scheme is executed in MATLAB software (The Math- Works, Natick, Massachusetts, USA) by loading the simulation data. Comparative evaluation of the proposed RVM based scheme with the existing support vector machine (SVM) based scheme clearly indicates the superiority of the proposed scheme in terms of decision speed (faster than SVM based scheme) and classification accuracy (more than 99%). Moreover, it does not operate under different types of external faults and system disturbances. Subsequently, the proposed scheme remains stable during severe current transformer (CT) saturation condition.

Development of an Active Power Reserve Management Method for DC Applied Wave-Wind Combined Generation Systems

A system that combines a wind turbine and a wave generator can share the off-shore platform and therefore mix the advantages of the transmission system construction and the power conversion system. The current hybrid generation system considers output limitation according to the instructions of the transmission system operator (TSO), and controls the profile using wind turbine pitch control. However, the integrated wave generation system utilizing a DC network does not adapt a power limitation scheme due to its mechanical constraints. In this paper, a control plan focusing on the electrical section of wave generators is formed in order to effectively manage the output profile of the hybrid generation system. The plan pays attention to power reserve flexibility for the utility grid using the analysis of the controllable elements. Comparison with the existing system is performed based on real offshore conditions. With the help of power system computer aided design (PSCAD) simulation, the ability of the novel technique is estimated by proposing the real power control based on the reference signal of TSO and the reactive power capacity it produces.

A new decoupling method for asymmetry‐parameter quadruple‐circuit lines on same tower

Quadruple‐circuit lines with different self‐impedances have been applied in power system with the development of power industry. However, the different self‐impedances in quadruple‐circuit lines will cause problems in fault analysis and related relay protection in the lines. The impedance matrix of these lines is different from that of symmetrical lines, and existing methods cannot completely eliminate all mutual impedance. A new method is proposed to decouple these asymmetrical quadruple‐circuits lines in this paper. The phase‐to‐phase mutual impedance is eliminated first, and then the line‐to‐line mutual impedance is eliminated according to the circulating current method. The mathematical deduction is formulated to ensure the complete decoupling of the impedance matrix. The fault conditions can be used to obtain the relationship between the independent sequence networks, which can be used to calculate the fault current. Power Systems Computer Aided Design (PSCAD) simulations indicate that the decoupling method is suitable for fault analysis of the quadruple‐circuit lines with different self‐impedances. The related fault analysis method is quite accurate and easy to be applied. The fault analysis accuracy is not affected by the fault resistance, fault type, fault location, or length of lines. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Effects of Unified Power Flow Controller (UPFC) on Distance Relay Tripping Characteristics in the North-Central Nigerian 330kv Network

This paper investigates the effects of UPFC on Distance Relay tripping characteristics in Nigerian 330kV (North-Central) Network. Its operation is based on impedance measurement at the relaying point. However, the system performance is often impeded by certain operational or structural factors such as load angle, the voltage magnitude ratio at the line ends, pre-fault line loading and short circuit levels at the line ends. The Unified Power Flow controllers (UPFC) incorporated into the Nigerian 330kV (North-Central) Network was modelled in the environment of Power System Computer Aided Design (PSCAD) and kept within the protected zone of the relay to increase the Apparent Resistance causing the relay to malfunction. Therefore, it is deduced by simulation analysis that the presence of UPFC in a faulted transmission line loop, protected by distance relay greatly affects the trip boundaries of the distance relay by setting it to either an over reaching or an under reaching state. Hence, the tripping characteristics of distance relay with UPFC located at various points with respect to a fault on a transmission line culminated in three scenarios whose results were presented and discussed in this paper. http://dx.doi.org/10.4314/njt.v34i4.18

Impact of DG different types on the grid performance

Distributed generation (DG) is playing an important role in power system to improve the grid performance. Optimizing the locations of DGs is necessary to enhance the Grid performance and to avoid the degradation of the power system networks. The type of DG directly influences the penetration level and the placement of DG. In this study, genetic algorithm (GA) technique is proposed to find the optimum location for three different types of distributed generation, these types are synchronous generator, wind turbine and photovoltaic. The obtained results are also validated using Particle Swarm Optimization (PSO). Three different types of DGs will be penetrated individually to find their optimum location and investigate their impact on the grid performance. This approach will be applied on IEEE 13 bus system which is simulated using Power System Computer Aided Design (PSCAD) and Matlab software. GA and PSO are used to find the optimum solution of multi-objective function; the objective function combines the overall number of buses experience voltage sag, the number of buses experience voltage drop, the number of buses experience voltage less than 10%, the overall number of buses experience voltage swell and network power loss. Finally, results are analyzed, discussed and validated which show that the optimum locations of each DG will vary according to the type of DG but all of them will be around the load center. In the mean time, results showed that the highest grid overall performance was for synchronous generator DG and the lowest for photovoltaic DG.

Performance of Distributed Generation (DG) towards Dynamic Voltage Restorer (DVR) in Mitigating Voltage Dips

This article presents the performance of Distributed Generation (DG) towards Dynamic Voltage Restorer (DVR) in mitigating voltage dips. An investigation was conducted to explore the effect of DG with the test system and the results will be analyzed during line to ground fault with DVR contains DG and without DG. The percentages of the voltage dips that occur will be compared between all the test systems. From this analysis of voltage dips percentage, the effectiveness of the DG towards DVR in mitigating voltage dips can be obtained clearly. The simulation of the test system will be done using Power System Computer Aided Design (PSCAD) software.

Optimal placement of unified power flow controllers to improve dynamic voltage stability using power system variable based voltage stability indices.

This study examines a new approach to selecting the locations of unified power flow controllers (UPFCs) in power system networks based on a dynamic analysis of voltage stability. Power system voltage stability indices (VSIs) including the line stability index (LQP), the voltage collapse proximity indicator (VCPI), and the line stability index (Lmn) are employed to identify the most suitable locations in the system for UPFCs. In this study, the locations of the UPFCs are identified by dynamically varying the loads across all of the load buses to represent actual power system conditions. Simulations were conducted in a power system computer-aided design (PSCAD) software using the IEEE 14-bus and 39- bus benchmark power system models. The simulation results demonstrate the effectiveness of the proposed method. When the UPFCs are placed in the locations obtained with the new approach, the voltage stability improves. A comparison of the steady-state VSIs resulting from the UPFCs placed in the locations obtained with the new approach and with particle swarm optimization (PSO) and differential evolution (DE), which are static methods, is presented. In all cases, the UPFC locations given by the proposed approach result in better voltage stability than those obtained with the other approaches.

T pattern fuse construction in segment metallized film capacitors based on self-healing characteristics

The breakdown happens in metallized polypropylene film (MPPF) capacitor can be classified into two cases: the first one is self-healing, which means that the insulation will recover after the breakdown; the other one is self-healing failure, which means that the capacitor will fail because of short-circuit fault. In this paper, the MPPF capacitor applied in DC filtering which adopt the T pattern segment film technology is investigated. To simulate the two cases mentioned above, a model based on self-healing experiment data is built by Power Systems Computer Aided Design (PSCAD). The current density flowing through the fuse and fuse energy is calculated and analyzed. Meanwhile, the fuse burn-out criteria are investigated according to electrical explosion theory and phase transition energy of segment metallized film fuse. The fuse design methodology of T pattern segment film is presented and a design case is provided.

A Novel Flow Invariants-Based Approach to Microgrid Management

This paper presents a novel flow invariants-based approach to microgrid management that is much more intuitive, less complex, and highly scalable in comparison with existing droop control, agent-based, and model predictive control-based approaches. These proclaimed advantages are exemplified by using a renewable energy-based microgrid (a microgrid-in-a-container) for a military forward operating base camp as the model system. The ability of the proposed approach to maintain the overall system stability and valid power flows while efficiently managing distributed energy resources through multiple operational modes is reflected by using a requirements matrix, and proven techniques in distributed systems and formal analysis. A Power System Computer Aided Design (PSCAD) simulation is used to validate and verify the real-world practicality of the proposed control approach.

Algorithms for fault zone detection in series‐compensated transmission lines

This study represents four new methods for fault zone detection in series-compensated lines and compares them with each other and with some previous methods. Among the proposed methods, two methods are based on direct current component of voltages and currents, and operate using both line ends data. The third method uses only one end data and is based on the analysis of instantaneous current behaviour. The fourth method also uses one line end data and acts on the basis of instantaneous power waveform behaviour. The proposed methods, besides the three well-known previous methods, are evaluated using a large number of simulated cases by power system computer-aided design. The results verify the validation of the proposed methods.